Rotary lobe pumps are well known industrial pumps which have been in common use for about forty years. A pair of counterrotating interlocking lobe rotors in a pump chamber draw fluid from an input port and expel the fluid through an output port. The pump is well suited to low velocity, high density fluid, especially sludge-like fluid. Examples of applications are chemical slurries, milk and sewage.
In operating environments where the pump is subjected to non-uniform material or fluid to be pumped, maintenance requirements increase substantially. For example, when pumping waste material, pieces of solid matter can be mixed in and get caught in the pump. When this happens, the pump is jammed and will stop as a result of the pump drive motor overload protection circuit. Once the pump has been jammed, the jamming object must be removed and the pump must be restarted. Also, certain waste products are especially harmful either to the rotor material (usually surfaced with rubber) or the seals around the rotor drive shafts. Caustic substances and precipitous liquid are examples of substances which are harmful to the seals, and fibrous material, such as paper pulp in municipal sewers, is an example of a substance which is damaging to the rotor surfaces, as well as the pump chamber.